210 ^ I THE LIFE OF PASTEUR 



which produce in one year more than 100,000 hectolitres of beer. 

 The great French savant was most courteously received by the 

 managers of one of the most important breweries in London, 

 who offered to show him round the works where 250 men were 

 employed. But Pasteur asked for a little of the barm of the 

 porter which was flowing into a trough from the cask. He 

 examined that yeast with a microscope, and soon recognized 

 a noxious ferment which he drew on a piece of paper and 

 showed to the bystanders, saying, " This porter must leave 

 much to be desired," to the astonished managers, who had 

 not expected this sudden criticism. Pasteur added that surely 

 the defect must have been betrayed by a bad taste, perhaps 

 already complained of by some customers. Thereupon the 

 managers owned that that very morning some fresh yeast had 

 had to be procured from another brewery. Pasteur asked to 

 see the new yeast, and found it incomparably purer, but such 

 was not the case with the barm of the other products then in 

 fermentation ale and pale ale. 



By degrees, samples of every kind of beer on the premises 

 were brought to Pasteur and put under the microscope. He 

 detected marked beginnings of disease in some, in others merely 

 a trace, but a threatening one. The various foremen were sent 

 for; this scientific visit seemed like a police inquiry. The 

 owner of the brewery, who had been fetched, was obliged to 

 register, one after another, these experimental demonstrations. 

 It was only human to show a little surprise , perhaps a little im- 

 patience of wounded feeling. But it was impossible to mistake 

 the authority of the French scientist's words : " Every marked 

 alteration in the quality of the beer coincides with the develop- 

 ment of micro-organisms foreign to the nature of true beer 

 yeast." It would have been interesting to a psychologist to 

 study in the expression of Pasteur's hearers those shades of 

 curiosity, doubt, and approbation, which ended in the 

 thoroughly English conclusion that there was profit to be made 

 out of this object lesson. 



Pasteur afterwards remembered with a smile the answers 

 he received, rather vague at first, then clearer, and, finally 

 interest and confidence now obtained the confession that 

 there was in a corner of the brewery a quantity of spoilt beer, 

 which had gone wrong only a fortnight after it was made, and 

 was not drinkable. "I examined it with a microscope," said 

 Pasfceur, "and could not at first detect any ferments of 



